David Waboso CBE, capital programmes director at London Underground, admitted there is still much to do.

He said: ‘We are investing millions to keep temperatures cool for passengers. New air conditioned trains are now operating on the Metropolitan, Circle, Hammersmith & City and are currently being rolled out on the Wimbledon to Edgware Road branch of the District line.

‘But we know there is still much to do and cooling the other deeper lines of the Tube remains a considerable engineering challenge. However, we are making significant steps and Londoners should be assured that we are not complacent about finding solutions.’

Cosy (Picture: Oli Scarff/Getty Images)

In the meantime, here’s the Government’s official advice on transporting animals – which should apply to humans.

‘High temperature and humidity can pose a major threat to animal welfare, especially when conditions change suddenly. It is therefore important that animals have access to shade and water, and are regularly inspected.

‘When transporting livestock, you should take appropriate measures to help you avoid problems in hot weather.’

These measures include:

Factoring potential weather conditions into your journey plan, e.g not loading or moving animals during the hottest part of the day